Localisation of damage in reinforced concrete structures by dynamic system identification

Service loads, environmental and accidental actions may cause damage to constructions. Regular inspection and condition assessment of engineering structures are necessary so that early detection of any defect can be made before major repair costs. When the structural damage is small or it is in the interior of the system, its detection cannot be done visually. A useful more elaborate non-destructive evaluation tool is vibration monitoring. It relies on the fact that occurrence of damage or loss of integrity in a structural system leads to changes in the dynamic properties of the structure. In this paper, different techniques will be presented and compared to derive from experimentally determined modal characteristics of a reinforced concrete beam its dynamic bending stiffness. The degradation of stiffness, due to the cracking of the reinforced concrete, gives information on the position and intensity of the occurred damage.